The present disclosure relates generally to the field of lithium-ion batteries and battery modules. More specifically, the present disclosure relates to Si-based anode materials for lithium-ion batteries.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Silicon (Si), as an anode material for lithium-ion batteries, offers a theoretical capacity that is approximately ten times that of the present commercial graphite anodes. However, typical Si anodes have a low cycle life due to the stresses associated with the large (e.g., approximately 300%) change in volume as lithium ions are transported into and out of the Si anode material, which results in cracking and eventual pulverization of the Si anode over repeated charging and discharging cycles. One strategy to address this cycling performance issue is to use Si/carbon (C) composites or Si—C alloys; however, the C can limit the capacity of the anode. Another strategy is to use porous Si structures with sufficient voids to directly buffer the volume change upon lithiation.
Porous Si structures, such as hollow Si particles, are typically synthesized using conventional templating materials, such as carbon, surfactants, and silica (SiO2). Removal of carbon/surfactant templates usually involves combustion in an oxygen-rich atmosphere, which leaves residual C impurities on the surface of the Si structures. In particular, the residual C impurities may be concentrated at the inner walls of the porous Si structures, and may prevent the Si structure from expanding inward upon lithiation, leading to a poorer cyclic performance of the Si anode. Furthermore, exposing Si structures to an oxygen-rich atmosphere (or using silica as a template material) can also oxidize a substantial portion of the Si to silica (SiO2), and SiO2 may react with Si at elevated temperatures to form other SiOx species. The high SiOx content of the resulting Si structures can also diminish the performance of a Si anode. Additionally, prior to the present disclosure, the synthesis of hollow or porous Si structures typically involved the use of certain chemicals, such as hydrofluoric acid (HF), magnesium (Mg), and cetyltrimethylammonium bromide (C19H42BrN), which can pose additional cost in handling and waste disposal as well as hinder large-scale production of hollow Si structures using these techniques.